108 Observations on the Natural History 
air-tubes, all shew, that in this animal none of those arrange- 
ments exist, which nature has instituted with such great solici- 
tude and skill in other reptiles, to carry on with ease and cer- 
tainty the respiratory function. But it is needless to multiply 
arguments, to prove that the air-bladders of these animals in no- 
wise perform the office of lungs, since it has been already shewn 
that, when taken out of the water, they die just as tishes do. 
M. Cuvier justly observes, that those animals can alone be 
deemed truly amphibious, 46 qui respirent, a la fois, fair elas- 
tique en nature, et celui qui contient feau and he then goes 
on to state, that the sirena lacertina respires through its whole 
life by lungs and by gills, and is therefore a permanently am- 
phibious animal ; but that the larvae of other reptiles make use 
of these two different organs only for a short period, and are 
therefore only temporarily amphibious. With all due respect, 
however, to so great a zoologist, we, say the authors, are of 
opinion, that before pronouncing the siren to be permanently am- 
phibious, it would have been proper to have made upon it, or 
upon animals which resemble it, experiments similar to those we 
have made on the proteus. If, in his researches with regard 
to ambiguous reptiles, he had not contented himself with exa- 
mining only their skeletons, but had examined also the larva, 
of the salamander, while yet alive, we are certain that his in- 
vestigations would have conducted him to opinions entirely op- 
posite to those which he has been led to form. 
In our investigations on this point, we have directed our 
attention to the above mentioned larvae, to observe particularly 
the changes which occur in their intimate structure, when they 
are transformed into perfect animals *. Between the siren and 
these larvae there is the greatest resemblance, not only in regard 
to the structure of the branchial arches, but also to the nostrils; 
for, in the siren, as well as in these larvae, the nostrils do not 
* The investigation here referred to, is contained in a memoir, entitled, 
“ Descrizione Anatomica degli organi della circolazione delle Larve delle Sala- 
mandre Aquatiche, fatta dal Dott. Mauro Rusconi,” Pavia, 1817. The substance 
of this memoir, we may, on a future occasion, communicate, from a belief that 
few questions, either in a zoological or physiological view, possess greater interest, 
or are at present less clearly understood, than the structure and transformation 
of these supposed amphibious reptiles.— T rans l. 
